Formula 1000 Race Car Blog

Category Archives: Suspension

The ends of the steering rack have to be in line with a plane through the control arm attachment points, and unless you have a custom-made rack this will require extensions to each end of the rack. I got these made and then went to the local nut & bolt emporium, only to find they don’t carry 3/8-24 socket-head cap screws. I know, weird huh? Had to order them on Ebay in the US and am now keeping my fingers crossed that they will arrive (at all). I recently ordered some more left-handed nuts the same way and they arrived in eight days with no problems, so yay?

We’re using Honda Civic wheel hubs, wheel bearings, CV joints and axle halfshafts. They’re available everywhere, cheap, and light, and by using them we avoid having to cut matching pairs of splines. The wheel hubs are drilled for lightness and tapped to accept the wheel drive pins, then the two outermost pieces from two scrap CV joints are cut down to use as bearing retainers for the front wheels. Rear axle halfshafts are used in stock form, but extenders from the halfshafts to the differential will have to be fabricated later.

When cutting the CV joints I found that the contact faces are hardened some way into the joint, making cutting almost impossible (by which I mean “impossible”) beyond a certain point, even with carbide cutting tools. If they are heat-treated, maybe there’s some way to reverse the hardening? It’s probably something more exotic than that, though, as the hardening was highly location-specific.

Starting to modify the wheel hubs. Mounted on the rotary table on the milling machine.

Drill…

Hand tap…

Finished wheel drive pin modifications

Wheel drive pins and brake hat fit! Note how the brake hat has been reduced to a lightweight spider.

Test fitting into front brake disc, inner view

Test fitting into front brake disc, outer view

Cutting the seat for the stub axle; adding more lightness.

Dowel-pinned the stub axles to the wheel hubs so they don’t turn when removing lug nuts.

Next step in getting the car rolling is to mount the steering rack. These parts were not laser cut but were cut with angle grinders and my bandsaw, because they’re, um, a design improvement. Yeah, a design improvement, that’ll work. It took me months to find a blade for my bandsaw, because Thailand. Anyway, now it’s useful for these kinds of tasks.

Once again we have something that looks simple, but took a great deal of thinking to arrive at. As Steve Jobs said, “Simple can be harder than complex: You have to work hard to get your thinking clean to make it simple.” I used to do almost exactly what Steve Jobs did; in fact, he once called my boss to persuade him to cancel the design we were working on, because Jobs was going to do it better (he didn’t). So I understand precisely what Jobs meant about simplicity. That might help explain why this was my fifth complete design for this subassembly. One downside of mechanical design: when you’ve sweated out an elegant design, anybody can take a casual glance at it and say “OBviously”. To which I reply, “OK, there’s probably an even better design out there somewhere. Let’s see you find it.”

Also attached are a few of the finite element analysis (FEA) tests that I performed to verify and improve this design.

Above you’ll see that my welding continues to improve, although slowly. In response to the deleted commenter of the day, yes, we do use dyslexic dwarfs to do our welding, but we get ours from Lithuania. Good guess, though!

Next we have photos of the rear suspension rocker arm mounts. As these have to be positioned correctly in three dimensions and three axes, and none of those are X, Y, or Z, it took about a week to get these fabricated and fitted. Starting with laser-cut pieces proved useful as that gave me a known-good shape to start from, but some of the frame rails could be a few millimeters off. Also, every time I weld on something it distorts. Both halves of the rocker arm mounts must be precisely concentric and exactly the correct distance apart. Unfortunately they are not connected directly to each other in order to allow for rocker arm movement between them so there’s plenty of opportunity for them to move, even though I did the welding with the rocker arm shafts in place. In the photo with the control arms installed, you’ll see one answer to that: a long piece of steel rebar turned to fit inside the rocker arm shaft bores. Pounding on that with a rubber mallet would move the bores back into alignment a bit at a time.

Positioned and held in place with bungee cords, ready for welding

Welding finished

Control arms, springs, shocks & rocker arms installed for the first time

Also, nose mounts. In the end these look terribly simple, but it took me a lot of thinking about how to do this. They have to be strong enough in one direction to lift the nose of the car with a pivoting jack, and in the other direction they have to support the downforce of the front wing. Also, they can’t protrude or be sharp so as not to injure another driver in a crash while taking the tremendous force of a forward impact, and have to allow the nose to be adjusted in three dimensions and two axes for proper body fit. Body installation begins here; the rest of the body will be keyed off the nose.

I received my second batch of laser-cut parts, this time from a new supplier that has some more reasonable aluminum. They did a reasonable job, but man were they slow. It took three visits and more than two weeks to get a quotation, then I forget how long to do the work. Then when they were finished, I had to call them to find out. This is Thailand.

The parts are cut from both steel and aluminum of several different thicknesses, and include the radiator and oil cooler mounts, differential mounts, some engine mounts, the entire pedal cluster, parts of the steering column, chain tensioner, nose mounts, steering rack mounts, steering column mounts, lap belt mounts, chassis side panels, seat panels, the firewall, fuel tank, and even an idler sprocket.

The upper control arms are all identical except that the bearing cups are mirrored from the left to the right so that the snap rings are on the bottom. If I can find a way to stake the spherical bearings then all four could be identical. Staking is a process that uses a hydraulic press to deform the bearing cup into a chamfer around the circumference of the spherical bearing, holding it permanently in place.

I printed out the layout of both control arms onto size A0 paper, glued the paper to a sheet of plywood, and drilled holes for the centerlines of each rod end and spherical bearing. This gives me a jig I can use for tack welding the parts in place. Washers under the bearing cups locate them vertically for tacking. The bearing cups proved a little too thin to weld without distortion, so I had to re-cut the spherical bearing bores after welding. Luckily I have an indexable end mill of just the right diameter, and running my mill at high speed with a lot of coolant gave a good finish on the bores. I then pressed the spherical bearings into place before painting as I wanted to make sure there were no glitches that would require messing up the paint to fix.

I sprayed Jotun Penguard 2-part epoxy paint directly onto the steel after first making sure the steel was scrupulously clean with a Scotchbrite pad on an angle grinder, followed by a cleaning with acetone and paper towels. The finish came out beautifully.

I was always dreading having to machine steel. I had to do it slowly to keep the temperature down and avoid chatter, even though I use carbide cutter inserts. Then I read somewhere that home hobbyists tend to be afraid to run the lathe & milling machine at high enough RPM to keep the cutting inserts happy, but if they do it will cause the insert to overheat and be cooked in two seconds. I figured I can find the cojones to run my equipment at maximum speed as well as the next guy…

So one day I was browsing at my new favorite store, Hardware House in Rayong, and I saw a gallon container of cutting coolant fluid for sale. I’d had no idea of how to find this stuff in Thailand, or even how to ask for it, so it was pure luck to stumble over it. Or you could call it diligence in going up and down every aisle in Hardware House looking for things I might need. They also had flexible fluid squirters and 12-volt water pumps, so I put together my own fluid cooling system, pictured above. I drive the pump with an automotive battery charger which allows me to reduce the voltage and amperage to get the correct flow, and it works like a charm! Now I can cut steel like I used to cut aluminum.

I found a local place that builds custom radiators for less than I paid for a used one on Ebay in the US.

Custom-built radiator, rear view

Positioning the front upper A-arm mounts

Positioning the rear upper A-arm mounts with jig

Pressing the suspension rocker arm bearings into place with my homemade press